The following disclosure is based on German Application No. 19951767.3, filed on Oct. 27, 1999, the disclosure of which is incorporated into this application by reference.
The present invention relates to a method for offering a phantom target for the protection of land, air or water vehicles or the like as a defense against missiles possessing a target seeking head operating in the infrared (IR) or radar (RF) range, or a target seeking head simultaneously or serially operating in both wavelength ranges. The invention furthermore relates to a combined RADAR/IR decoy.
A threat owing to modern, autonomously operating missiles is clearly increasing, inasmuch as even missiles having leading-edge target seeking systems are becoming wide-spread as a result of the collapse of the former superpower, the Soviet Union, and of liberal export regulations particularly by Asian countries. The target seeking systems of such missiles operate mainly in the radar (RF) and infrared (IR) ranges. Herein both the radar backscattering behavior and the emission of specific infrared radiation from targets, such as ships, aircraft, tanks, etc. are made use of for target location and target tracking. In leading-edge missiles, the development clearly presents a trend towards multispectral target seeking systems simultaneously or serially operating in the radar and infrared ranges in order to be able to perform an improved false-target discrimination. For the purpose of false-target discrimination, multispectral IR target seeking heads operate with two detectors that are sensitive in the short-wave and long-wave infrared range. So-called dual mode target seeking heads operate in the radar and infrared ranges. Missiles possessing such target seeking heads are radar controlled in the approach and seek phases and switch over to, or add on, an IR seeking head in the tracking phase.
One target criterion of dual mode target seeking heads is the so-called co-location of RF backscattering and of the IR center of radiation. Comparison of co-ordinates being possible, discrimination of false targets (e.g. clutter, such as older decoy types) is improved. The optimised co-location of RF and IR efficiency is therefore an indispensable prerequisite for a dual mode decoy in order to enable effective deception of modern dual mode target seeking heads, i.e., their diversion from a target to be protected to a phantom target. Herein merely the smallest possible resolution cell of the target seeking head (RF and IR) is of relevance for co-location.
A first successul method for the diversion of weapons possessing dual mode target seeking heads approaching the object to be protected is described in German patent specification DE 196 17 701, which corresponds to issued U.S. Pat. No. 5,835,051.
In this prior art, a mass which emits radiation in the IR range (IR effective mass) and a mass which backscatters RF radiation (RF effective mass) are simultaneously made to take effect in the appropriate position as a phantom target.
As an RF effective mass in the prior art of DE 196 17 701, rolled-up radar chaff that comprises dipoles of aluminum or silver coated glass fiber filaments having a thickness of approx. 10 xcexcm to 100 xcexcm are used and employed in a number of more than approx. 106 dipoles/kg.
IR flares, known, e.g., from German Patent DE-PS 43 27 976 and its corresponding U.S. Pat. No. 5,635,666 and emitting a medium-wave radiation component (MWIR flares), are preferably employed as the IR effective mass.
In accordance with the prior art of DE 196 17 701, the effective masses are placed in a projectile having a caliber, for example, in the range of about 10 to 155 mm.
In accordance with DE 196 17 701, the effective massesxe2x80x94including activating and distributing meansxe2x80x94are jointly ejected from a projectile shell and successively activated and distributed during the in-flight phase of the projectile by means of a deployment element.
Thus it is achieved that the effective masses are deployed without any screening so that no excessive pressure acts on the effective masses during their distribution. Accordingly, the distribution of the IR effective mass and in particular the distribution of the RF effective mass may already be improved considerably. Activation of the IR effective mass is moreover clearly improved, whereby the effectivity of the IR effective mass in terms of radiation intensity per volume unit as well as in terms of radiating surface is increased in comparison with methods not providing for ejection of the effective masses.
In accordance with the prior art of DE 196 17 701, it is generally provided to use a propellant charge for ejection of the deployment element, which propellant charge is ignited by an ignition delay means which is ignited by combustion of an ejection propellant charge for the projectile.
Preferably the ejection propellant charge for the deployment element is ignited by means of a pyrotechnical ignition delay means.
Moreover in the prior art an igniting and ejecting unit centrally arranged in the deployment element is used as activating and distributing means for activating and distributing the IR effective mass and for distributing the RF effective mass.
Herein it may be provided for igniting and ejection to make use of a pyrotechnical charge ignited by an ignition delay means which is ignited by combustion of the ejection propellant charge for the deployment element.
As a pyrotechnical charge, aluminum/potassium perchlorate or magnesium/barium nitrate is generally used.
In the prior art, effective masses annularly arranged around the igniting and ejecting unit are used.
In particular the igniting and ejecting charge is employed in an amount adapted to the number and cross-section of the utilised ejection openings in such a manner that high acceleration forces do not act on the effective masses. Namely, the amount of the igniting and ejecting charge in proportion to the number and cross-section of the ejection openings determines the combustion velocity of the igniting and ejecting charge. At an identical quantity of the charge, the combustion velocity increases concomitantly with a decrease of the overall cross-section of the ejection openings. By selecting a quantity of the igniting and ejecting charge in accordance with the invention, it is ensured that a uniform thrust is exerted on the effective masses, rather than an abrupt impulse corresponding to an explosion.
This does ensure better ignition and distribution of the IR effective masses and a better distribution of the RF effective mass in comparison with conventional explosion principles. However the following problems or drawbacks, respectively, still result:
1. The diameter of the RADAR effective masses on a dipole basis, which are mostly deployed spherically, is sometimes too large to be located entirely inside the range gates of the RADAR target seeking heads.
2. Activation of the RADAR effective masses may take place outside the range gate, making them invisible to the target seeking head and therefore ineffective.
3. The large diameter of the deployed dipole effective masses results in an excessively low dipole density at the outer limits of these prior art effective masses. Density distribution herein corresponds roughly to a Gaussian distribution with a gradually increasing density towards the effective mass center, without the required contouring relative to the background echo.
4. The dipoles of the standard RADAR effective masses assume a horizontal orientation after about 5 seconds and absorb/emit the horizontal component of a radar wave exclusively. Target seeking heads possessing a vertically polarised RADAR are therefore capable of discerning these dipoles.
5. Both the RADAR and IR effective masses are mostly distributed within hard metallic receptacles by means of a detonator charge, resulting in disintegration fragments which may cause considerable damage when the decoy is discharged at minimum range, e.g., of a ship (in the range gate of the target seeking head).
Embarking from the prior art of DE 196 17 701 and corresponding U.S. Pat. No. 5,835,051, it is therefore an object of the present invention to furnish an improved method and an improved decoy avoiding at least one of the above described drawbacks.
According to one formulation, the invention is directed to a method for offering a phantom target for protecting an object against at least one missile possessing both a first target seeking head operating in the infrared (IR) wavelength range or in the radar (RF) wavelength range and a second target seeking head operating simultaneously or serially with the first target head in both of the wavelength ranges. The method includes: causing an effective mass emitting radiation in the infrared range (IR effective mass) based on flares and an effective mass backscattering radiation in the radar range (RF effective mass) based on dipoles to take effect simultaneously in a given position, as a phantom target. A ratio of dipole mass to flare mass in a range of about 3.4:1 to about 6:1 is employed. The flares present a descent rate about 0.5 to 1.5 m/s higher than a descent rate of the dipoles.
In terms of device technology, the object is attained by means of a combined radar-infrared decoy including a decoy body and dipoles and flares contained in the body in a ratio of about 3.4:1 to about 6.0:1, whereby the flares, following disintegration of the decoy body, present a descent rate which is about 0.5 m/s to about 1.5 m/s higher than the descent rate of the dipoles.
Thus, the invention relates to deployment of a dual mode decoy and to the decoy itself. Dual mode decoys having concurrent RADAR and IR efficiency utilizing combined RADAR/IR effective masses, as well as the associated effective masses, are known from DE 196 17 701 and its corresponding U.S. Pat. No. 5,835,051. Given their relevance to the present application, the full disclosures of these two references are incorporated into the present application by reference.
By employing a ratio of dipole mass to flare mass of approx. 3.4:1 to approx. 6:1 and by using flares that present a descent rate that is approx. 0.5 to 1.5 m/s higher than that of the dipoles, it is achieved that the dipoles are swirled by the thermal upcurrent as a result of combustion of the flares. This avoids an exclusively horizontal orientation of the dipoles and instead produces a statistical orientation, so that, on the whole, the desired RADAR omnipolarity is produced.
The required descent rates of the flares may be adjusted through size and shape of the flares on the one hand, and through the mass per unit area of the flares used, on the other hand.
Geometrical flare shapes which were found to be favorable for the purposes of the present invention include semicircular, quarter-circle and trapezoidal shapes.
The radius for the partially circular flares is preferably approx. 60 to 130 mm. With such flares, the descent rate of the burning flares may be adjusted to approx. 1.5 m/s to 2.5 m/s, so that the flares generating hot exhaust gases present a descent rate which is by approx. 0.5 to 1.5 m/s higher than that of the dipoles.